1. Field of the Invention
This invention relates to the insecticide carbofuran and to its use in soils where its insecticidal activity declines upon repeated applications. In particular, this invention relates to means of restoring the insecticidal activity of carbofuran in such soils.
2. Description of the Prior Art
"Carbofuran" is the common name for 2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate, which is represented by the following formula ##STR2##
This compound is claimed in U.S. Pat. Nos. 3,474,170 and 3,474,171, both issued on Oct. 21, 1969, to W. G. Scharpf, and both assigned to FMC Corporation. In addition to its common name, the compound is known to the public under the FMC Corporation trademark "Furadan.RTM." and the Bayer AG trademark "Curaterr.RTM.". In its technical form, the compound is a colorless crystalline solid. It is normally used, however, as a wettable powder containing 750 g active ingredient per kilogram, a flowable paste containing 480 g active ingredient per liter, or granules containing 20, 30, 50, or 100 g active ingredient per kilogram.
Carbofuran is a systemic insecticide, acaricide, and nematicide. It is applied to plant foliage at 0.25 to 1.0 kilograms active ingredient per hectare (kg/ha) for the control of insects and mites, broadcast at 6 to 10 kg/ha for the control of nematodes, or applied to soil (particularly seed furrows) at 0.5 to 4.0 kg/ha for the control of foliar-feeding and soil insects. The present invention is directed to the soil application.
In certain soils, repeated applications of carbofuran have produced successive decreases in insecticidal activity. With a sufficient number and frequency of applications, the insecticide can become totally ineffective. It is therefore an object of this invention to restore the insecticidal activity of carbofuran in soils where repeated application has either substantially lessened its activity or destroyed its activity altogether.